It is known to provide a variety of aerodynamic devices on the outer surface of wind turbine blades in order to improve the performance of the blade or, for example, to reduce noise levels produced by the blades in use. Typical aerodynamic devices include flaps such as Gurney flaps, vortex generators, and other trailing edge devices such as serrations.
The devices may be formed integrally with the outer shell of the blade, or they may be mounted to the blade shell. These devices are often generally referred to as ‘add-ons’, and may be provided on the blade during the blade manufacturing process, or later to existing blades as a retrofit.
The aerodynamic devices typically comprise a baseplate configured for mounting to the outer surface of the blade. The baseplate supports aerodynamic features such as flaps, turbulence producing formations and/or serrations. The baseplate is typically bonded to the outer shell of the blade by means of adhesive.
The blade add-ons should remain firmly secured to the blade during the service life of the wind turbine, which is typically twenty years or more. As the blade moves through the air at high speed when the rotor rotates, these aerodynamic devices experience significant forces. Any degradation of the adhesive may therefore present a risk of the devices being torn from the surface of the blade in use.
It is therefore important to ensure that the adhesive is not compromised during mounting of the add-ons and thereafter when the wind turbine is in use. Wind turbines are often exposed to harsh environmental conditions and experience extremes of temperature and other climatic conditions. It is important to protect the adhesive from exposure to these conditions, otherwise there is a risk that the adhesive may be compromised or degrade over time. In particular, it is desirable to prevent the adhesive coming into contact with moisture, dust and direct exposure to sunlight.
One solution to this problem is described in the applicant's European patent no. EP2027390, whereby sealant is provided at the periphery of a turbulence generating strip. The sealant serves to seal the edges of the device to the outer surface of the blade. The seal prevents ingress of moisture and dust between the surface of the blade and the device and thus protects the adhesive that bonds the strip to the surface of the blade.
However, when the sealant is initially applied, it may be difficult to prevent the sealant from coming into contact with the adhesive bonding the device to the blade surface. There is therefore a risk that the sealant may interfere with the adhesive bond between the device and the blade. The sealant also remains visible around the edges of the device, and thus is itself exposed to moisture and dust in use, which may cause the sealant to deteriorate over time.
Against this background, it as an object of the present invention to address at least one of these problems.